1. Field of the Invention
The present invention relates to an aromatic vinyl resin material and an aromatic vinyl resin molded product, and more particularly to an aromatic vinyl resin material that is endowed with excellent heat resistance, solvent resistance, toughness, tensile elongation, and transparency, and to an aromatic vinyl resin molded product thereof.
2. Related Art
Previously, the present inventors successfully developed a styrene polymer having a high syndiotacticity (Japanese Patent Application Laid-Open (kokai) Nos. 62-104818, 63-241009). The styrene polymer having a syndiotactic structure (hereinafter simply referred to as "syndiotactic polystyrene" or "SPS") is endowed with excellent heat resistance and solvent resistance, but does not exhibit sufficient toughness or elongation. In addition, it has poor compatibility with other resins; therefore its use has inevitably been limited. When SPS is used for producing a film that requires transparency, SPS is cooled rapidly from the molten state to acquire transparency. However, the thus-obtained film has a drawback in that it is brittle.
In order to overcome this drawback, the present inventors succeeded in endowing the aforementioned styrene polymer having a syndiotactic structure with toughness by copolymerizing styrene with an olefin (Japanese Patent Application Laid-Open (kokai) Nos. 3-7705, 4-130114, 4-300904).
However, the thus-obtained random or block copolymer of styrene and an olefin suffers insufficient controllability of the copolymerization composition as well as a low copolymerization-modification ratio (i.e., percentage of modifier olefins in the resultant copolymer), leading to insufficient improvement in toughness, elongation, and compatibility with other resins.
There have been proposed a large number of compositions in which a rubber-like elastic substance or thermoplastic resin is added to SPS (Japanese Patent Application Laid-Open (kokai) Nos. 01-146944 and 01-279944). However, due to lack of an effective compatibility-enhancing agent, dispersion of thermoplastic resin or the like is insufficient, resulting in deterioration in transparency.
There have also been proposed graft copolymers in which a styrene monomer is graft-copolymerized with a polymer bearing double bonds in side chains, as well as block copolymers in which a styrene monomer is block-copolymerized with a macromonomer bearing polymerization-active terminal vinyl groups (Japanese Patent Application Laid-Open (kokai) Nos. 05-247147 and 05-295056). However, the copolymers disclosed in the above publications are inhomogeneous in copolymer composition and exhibit insufficient graft ratio, resulting in insufficient improvement in targeted properties such as toughness, elongation, and impact resistance.
In view of the foregoing, an object of the present invention is to provide an aromatic vinyl resin material for producing a molded product which is endowed with heat resistance, solvent resistance, toughness, tensile elongation, and transparency, as well as to provide a molded product of the resin material.